The present invention relates generally to the method of heat transfer using a pulsating heat pipe (PHP), an apparatus and, for practical applications such as power engineering, chemical industry, heat recovery and ecological systems etc.
The first pulsating heat pipe was described as pulsating heat pipe (PHP) in the former USSR in 1971 by Smyrnov G. F. and Savchenkov G. A. (see USSR patent 504065, filed Apr. 30, 1971). Smyrnov G. F. made use of his inventions in refrigerating devices (see USSR patents 730047 and 1722117). The inventor (Smyrnov) in his doctorate dissertation, discussed the theoretical aspects (see Smyrnov G. F. xe2x80x9cThe evaporative thermal control systems fundamentalsxe2x80x9d, 1979. The thesis of Leningrad Institute of Refrigeration and Food Technologies.).
Lately, Akachi H. (Japan) suggested a new variant of the pulsating heat pipe constructions (U.S. Pat. Nos. 4,921,041, 5,219,020, 5,507,092, 5,642,775, 5,697,428). For example, in U.S. Pat. No. 4,921,041 Akachi H. wrote: xe2x80x9c. . . heat pipe is disclosed in which a heat pipe carrying fluid, preferably a bi-phase noncondensative fluid, circulates in a loop form in itself under its own vapor pressure at a high speed within a pipe so as to repeat vaporization and condensation, thus carrying out a heat transfer.xe2x80x9d Hereinafter in variants of design of the pulsating heat pipes, Akachi H. wrote: xe2x80x9cA check valve(s) propels and amplifies forces generated by the heat carrying fluid and its vapor to move towards the stream direction limited by the check valve(s) so that the heat carrying fluid circulates in the stream direction through the closed-loop passage defined by the pipe at the high speed, repeating vaporization at the heat receiving and radiating portions.xe2x80x9d
There are Limitations in the above Akachi Disclosures
1. Reliable start up of these devices independently of their position in the gravity field?
2. Differences in the forces, which ensure the stable movement of the two-phase flow of heat carrier?
Akachi""s explanation of the check valve(s) role in the influence on the two-phase flow movement is: xe2x80x9cA check valve propels and amplifies forces generated by the heat carrying fluid.xe2x80x9d This check valve allows flow in both directions under low flow conditions, but only in one direction with high flow. It is well known that a valve adds local hydraulic resistance, not forces to propel or amplify any forces. The Akachi patents outline that looped and non-looped pulsating heat pipes have the same method of action.
It is necessary also to note the inventions of Dinh K. (see U.S. Pat. Nos. 5,404,938, 5,845,702, and 5,921,315). He designed heat pipe heat exchangers on the base of the serpentine heat pipes. The practical application of these serpentine heat exchangers is for air conditioning systems, primarily, for improvement of the dehumidification process of cooling air. These devices consist of two parts (sections)xe2x80x94evaporation and condensation where there are the traditional refrigerants with considerable levels of pressure in the working regimes and also the traditional metallic materials for tubes with internal diameter considerable more than capillary sizes.
The following disclosure sets out the method and apparatus to accomplish efficient heat and mass transfer using the pulsating heat pipe, with stability and minimal mechanical components.
Object of the invention is to provide a pulsating heat pipe (PHP) method of action, construction and devices using these heat pipes. The suggested method of action of the PHP allows stability in processes of heat and mass transfer. The author""s disclosure outlines previously unknown action and processes, which can improve and increase efficiency of PHP. In accordance with the claims of the invention, this object is achieved by providing in the PHP special and selected irregularity (non-uniformities) of the geometric and physical nature. These lead to thermo hydraulic differences and in heat and mass transfer coefficients improvements. Additionally, periodically acting driving forces are generated and can be used by the apparatus to produce stability in the operation in some of the embodiments.
Another object of the invention is to provide in some embodiments a PHP design, which can be inexpensive and convenient for manufacturing. The design uses simple elements in the PHP, as bellows, capillary inserts, and small elastic parts of the branches of a channel and others, which can increase the reliability of PHP. The thermo hydraulic features result in lowering the average temperature difference between the heating and cooling zones due to the PHP stability and reliability.
Still another object of the invention is to provide the devices that are compact heat exchangers with and without fins, which can work independently from gravitation and gravitational orientation, and different heat transfer modules for heat dissipation in various environmental media, including radiation in space etc.